As someone who doesn't have the experience of mapping that you all do, but I do know something about public transport, I can see how the various concepts for single track and double track etc work along straightforward corridors (note these must be "tracks" (or maybe some other term) and not "lines" - as a "line" in public transport is something completely separate from the infrastructure) ... but what happens when operational details get more complicated ... at stations, or near and in depots and sidings? What happens for passing bays? Does a track have a directionality associated with it (even if it is only implied by a national convention of "driving on the left/right"... though that will give some issues on the German border where operations switch sides) - and what happens when multiple tracks are signalled for bi-directional working?
I sense that there is a potential issue here between describing the physical infrastructure and describing its functional performance ... and I am not sure the boundary has been drawn correctly between the two. Roger -----Original Message----- From: talk-transit-boun...@openstreetmap.org [mailto:talk-transit-boun...@openstreetmap.org] On Behalf Of Peter Miller Sent: 22 June 2009 10:31 To: Jochen Topf Cc: osm Subject: Re: [Talk-transit] Multiple tracks On 22 Jun 2009, at 07:51, Jochen Topf wrote: > On Sun, Jun 21, 2009 at 05:09:35PM +0100, Richard Mann wrote: >> No, simpler than that: >> >> tracks=1 => render a single line at all zooms >> tracks=2 => render a double line at all zooms >> tracks=X => render a multiple line with X tracks at all zooms >> tracks=1ofX => render a single line at high zooms, but render as if >> tracks=X >> at medium/low zooms > > But then you'd still draw several lines nearly on top of each other > in medium > zoom levels which doesn't look good, which was the problem we were > trying to > fix? > > Anyway, this is a rather specialized trick about rendering the > number of tracks > properly. But what if you want to render other attributes. Say one > of your two > tracks is an industrial railway, the other a normal passenger > railway and you > want to distinguish those types. On medium zoom levels, is this a > two track > thing and we loose the type distinction, or do we keep it? The dual_carriageway and Junction relations would appear to the a good way of doing such things. I realise that the 'dual carriageway' term is not right and that other work would be required on the specifications, however it would seem a better starting point. http://wiki.openstreetmap.org/wiki/Relations/Proposed/Junctions http://wiki.openstreetmap.org/wiki/Relations/Proposed/Dual_carriageways A group of parallel tracks would be combined using 'dual carriageway' and then a group short sections of track and nodes can be combined as a 'Junction'. The render would then have a choice of drawing modes, either a single line and single point, or multiple lines/points. Regards, Peter > > > Jochen > -- > Jochen Topf joc...@remote.org http://www.remote.org/jochen/ > +49-721-388298 > > > _______________________________________________ > Talk-transit mailing list > Talk-transit@openstreetmap.org > http://lists.openstreetmap.org/listinfo/talk-transit _______________________________________________ Talk-transit mailing list Talk-transit@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-transit _______________________________________________ Talk-transit mailing list Talk-transit@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-transit
